The Besting Spores of the Potato Fungus. By W. G, Smith. Ill 
of the Ascomyces, as illustrated at the last meeting of the Eoyal 
Horticultural Society. 
My opinion, therefore, was soon formed that the "new " Potato 
disease (as it has heen called) was no other than the old enemy in 
disguise, or, in other words, that it was the old Peronospora 
infestans in an unusual and excited condition. That climatic con- 
ditions had thrown the growth of this fungus forward and out of 
season was probable; but the idea that the pest would not at length 
attack all and every sort of Potato was to me most unreasonable, 
though the more tender sorts might be the first to suffer. 
Suspecting the two-sized small bodies before mentioned to be of 
the nature of spores, and remembering my experiments during last 
autumn with ketchup, in which I observed that the spores of the 
common Mushroom might be boiled several times, and for lengthened 
periods, without their collapsing or bursting, I thought I would 
try to set free the presumed spores in the Potato leaves by macera- 
ting the foliage, stems, and tubers in cold water. This maceration 
was necessary because the tissue of the diseased leaves was so 
opaque and corroded, and the cell- walls were so thickened, that it 
was difficult to distinguish the threads and suspected spores from 
the cellular tissue. I did not treat the leaves with boiling water, 
because I wished to keep the threads and spores alive. 
From day to day I kept the diseased leaves, stems, and tubers 
wet between pieces of very wet calico, in plates under glass, 
and I immediately noticed that the continued moisture greatly 
excited the growth of the mycelial threads ; this to me was quite 
unexpected, as I had merely wished to set the spore-like bodies free. 
So rapid was now the growth of this mycelium that after a week 
had elapsed some decayed parts of the lamina of the leaf were 
traversed in every direction by the spawn. Thinking the close 
observation of this mycelium in the now thoroughly rotten and 
decomposed leaves might end in some addition to our knowledge of • 
Peronosj)ora infestans, to which fungus I had no doubt from the 
beginning that the threads belonged, I kept it under close observa- 
tion, and in about ten days the mycelium produced a tolerably 
abundant crop, especially in the diseased tubers of the two-sized 
bodies I had previously seen and measured in the fresh leaves. 
The reason why these objects, which undoubtedly occur in and 
about the spots, are so extremely few in number in those positions 
is, I imagine, because they require a different set of conditions for 
their normal growth, and these conditions are found in abundant 
and continued moisture. 
The larger of these bodies I am disposed to consider the 
"oogonium" of the Potato fungus, and the smaller bodies I look 
upon as the "antheridia" of the same fungus, which are often 
terminal in position. The filaments of the latter are commonly 
